The computer itself is in less than good condition, so I wouldn't be surprised if it's a soundcard issue. It is only the speakers as far as I know that aren't working. I could try a reboot first, but anytime that computer gets turned off, it 50% of the time freezes on a blue error screen, and more often, it stops supporting USB supported mice (the only ones I have).
I'm probably going to have my dad look at it before I try that though, since he's been the one dealing with the issues more than I have.